Hi, I have a 2006 Chrysler 300c with 134,000 miles. I just replaced the front and back brakes for the first time. A week or so before the brakes were replaced the ABS started to activate on dry roads when I applied the brakes. This happened at any speed not just right before the car stopped. My mechanic wanted me to take it to the dealership and have it checked before the brakes were replaced. The dealer said the ABS was activating because the pads were low, so I took the car back to my mechanic and had the brakes replaced. Well the problem has not gone away. I took the car back to the dealership and they ran it on the computer and found nothing. So the next step was to install new brake sensors, but this also did nothing. The dealership said the next step would be to replace the wheel hubs at $225 per wheel, but they could not give any assurance that this would fix the problem. I decided to take the car to another mechanic that was recommended by my first mechanic. This new mechanic, did some checking and also could find nothing. They did offer to do some special testing with their scope but I would have to pay for the time spent, which could be from 1 hr to 8 hrs. I agreed to have them spend 2 to 3 hours and see what they could find. Once again nothing, they did agree with the dealership that wheels hubs would be the next step, but it may not fix the problem. Both the dealership and the 2nd mechanic are reluctant to replace the wheel hubs because they can not guarantee if it will fix the problem, nor do they know what hub is the problem so it’s a gamble. The brakes work fine, but I am a little scared to keep driving the car. Do I gamble $1000 on the hubs or look for a new car?
You need to find a good independent mechanic who understands the ABS system and can troubleshoot it thoroughly. I have one question since you already changed the ABS sensors: Do all 4 tires tread match in height and are they all of the same brand? Mismatched tires can cause problems with the ABS system. BTW…the last wheel hub that I bought for my Dodge Dakota (2005) cost about $100 per wheel. I looked yours up on rockauto and they were the same price. If you could do the job yourself or had a mechanically inclined friend…the cost would be greatly reduced.
The ABS is activating because it “thinks” a tire is slipping. The only way it can read this is to compare the wheel speed sensor signal right and left, front and rear to see which one is different and then reduce the brake pressure (activate ABS) to that wheel. It points to a problem with the speed sensors which you’ve had replaced. They want to replace the wheel hubs because the hub contains the sensor ring.
Given the mileage, I’d go ahead and replace the hubs, they are near the end of their life.
While they are replacing these parts have them check the ride height of the car. Make sure it is level and within specifications. The reason I suggest this is if the car has sagged a bit or has one broken spring, the force on one tire will be different that its twin on the other side and it may trigger the ABS just before the car comes to a stop. Sounds weird, but I’ve had this occur on an ABS equipped truck. Re-leveling the truck by adjusting the torsion bar fixed it.
Return to mechanic 1 and have him order one new hub for the right front and right rear and install those. He will probably be able to do them much cheaper than the dealers quote of @225 each.
Have him keep and mark the hubs that he removed.
Drive the car and if the light still goes on it must be the hubs on the left side, because they are original and have not been replaced. If the light stays off, you have found that it was one of the hubs on the right.
If the light comes back on, make another appointment for him to use the old hubs that he removed from the right side and put them on the left side.
Mechanic #1s labor will be much less, but you will be paying him to do all four, but you will only be buying 2 hubs.
Ask the dealer to swap out the ABS control module. If it fixes it then you will pay for it, if not then can reinstall your original ABS module. Only a dealer can return installed parts. Also, the brake switch has 2 separate inputs to the ABS module. I would check that also.
A road test with a scanner graphing all wheel speed sensors at the same time should show the bad sensor. Replacing the hubs on a W.A.G. can get expensive quick. The tech should be able to see which sensor has a variance compared to the others. There could also be a wiring problem or a brake ecu issue. A proper diagnosis is cheaper than guessing until you find the problem.